A New Force of Nature, an excerpt from Keepers of the Spring: Our Water in an Age of Globalization

There are today some 800,000 dams around the world. Some 45,000 of
them are more than 50 feet high; more than a hundred tower 500 feet
or higher above the rivers they are intended to tame. If all the
water in all the reservoirs behind all the dams in the world were
collected together, it would measure 8 billion acre-feet. It would
cover half of California to a height of 130 feet. If it were all
released into the oceans, it would raise the sea level on every
beach around the world by some 8 inches.

... Since 1900, the world has on average completed one large dam
every day. Their turbines generate a fifth of the world's
electricity, and their waters irrigate a sixth of the world's crops.
They barricade 61 percent of the world's river flows.

These dams have even changed the shape and rotation of planet Earth.
The water in their reservoirs is so heavy that it deforms the
Earth's crust and unleashes periodic earthquakes. And by shifting
water away from the equator, where ocean water is concentrated, they
have altered the speed of the Earth's rotation in much the same way
as ice skaters speed up by pulling their arms in close to the body.
The "reservoir effect" has so far shortened the length of
the day by about a thousandth of a second. The asymmetrical
distribution of reservoirs round the Earth has even tilted the
Earth's axis. The North and South Poles and every line of latitude
and longitude are now 2 feet from where they would otherwise have been.

Dams are more than an earth-shaping technology. They have great
power as totems of modernism and as symbols of a very mechanistic
notion of how mankind can "tame nature."

Keepers of the Spring: Reclaiming Our Water in an Age of GlobalizationFred PearceIsland Press, $26